Electronic Device, Multilayer Ceramic Capacitor and the Production Method Thereof

ABSTRACT

An electronic device, such as a multilayer ceramic capacitor, and a method for producing the electronic device having an internal electrode layer and a dielectric layer, comprising a step of forming a pre-fired internal electrode thin film including a conductive component and a dielectric component, a step of stacking green sheets to be dielectric layers after firing and the internal electrode thin films, and a step of firing a multilayer body of the green sheets and the internal electrode thin films are provided: by which grain growth of conductive particles in a firing step can be suppressed, spheroidizing in the internal electrode layers and breaking of electrodes can be effectively prevented, and a decline of the capacitance can be effectively suppressed even when a thickness of each internal electrode layer is made thinner.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic device, a multilayerceramic capacitor and the production method and, particularly, relatesto an electronic device and a multilayer ceramic capacitor capable ofresponding to attaining a thinner layers and downsizing.

2. Description of the Related Art

A multilayer ceramic capacitor as an example of electronic devicescomprises an element body having a multilayer structure, wherein aplurality of dielectric layers and internal electrode layers arealternately arranged, and a pair of external terminal electrodes formedon both ends of the element body.

The multilayer ceramic capacitor is produced by forming a pre-firedelement body by alternately stacking a plurality of pre-fired dielectriclayers and pre-fired internal electrode layers exactly by necessarynumbers, firing the result and, then, forming a pair of externalterminal electrodes on both end portions of the fired element body.

A ceramic green sheet, etc. produced by the sheet method or thestretching method, etc. is used for the pre-fired dielectric layers. Thesheet method is a method for producing by applying dielectric slurryincluding a dielectric powder, binder, plasticizer and organic solvent,etc. to a carrier sheet, such as PET, by using the doctor blade method,etc. and heating to dry. The stretching method is a method for producingby performing biaxial stretching on a film-shaped molded body obtainedby extrusion molding of a dielectric suspending solution obtained bymixing dielectric powder and a binder in a solvent.

The pre-fired internal electrode layers are formed by using the printingmethod for printing internal electrode paste including a metal powderand a binder on the ceramic green sheet explained above in apredetermined pattern, or by the thin film formation method usingplating, vapor deposition or sputtering, etc. to form a conductive thinfilm in a predetermined pattern on the green sheet. Particularly, whenforming by a conductive thin film obtained by the thin film formationmethod, the internal electrode layer can be made thinner, so that amultilayer ceramic capacitor can be made to be more compact and thinnerwith a larger capacity.

As explained above, when producing a multilayer ceramic capacitor, thepre-fired dielectric layers and pre-fired internal electrode layers arefired at a time. Therefore, a conductive material included in thepre-fired internal electrode layers is required to have a higher meltingpoint than a sintering temperature of the dielectric powder included inthe pre-fired dielectric layers, not to react with the dielectric powderand not to be diffused in the fired dielectric layers.

In recent years, along with downsizing of a variety of electronicdevices, multilayer ceramic capacitors to be installed inside theelectronic devices have become downsized and come to have a largercapacity. To attain such downsizing and a larger capacity of multilayerceramic capacitors, the internal electrode layers have been required tobe thinner as well as the dielectric layers. As a method of obtainingthinner internal electrode layers, a method of forming the pre-firedinternal electrode layers by a conductive thin film obtained by the thinfilm formation method may be mentioned (for example, the patent article1: The Japanese Patent Publication No. 3491639).

This patent article 1 discloses a production method of a multilayerceramic capacitor by forming a second metal layer including ceramicparticles by the composite plating method on a first metal layer formedby a thin film formation method. According to the production methoddisclosed in the article, by forming the second metal layer functioningas an adhesive layer in addition to the first metal layer to be aninternal electrode layer after firing, delamination of the internalelectrode layer and dielectric layer after firing can be prevented.

However, in this article, the second metal layer is an adhesive layerfor preventing delamination and formed by the plating method. Therefore,the second metal layer had to include dielectric particles in arelatively larger content, and the thickness had to be thick.

Also, as a conductive material to be included in the pre-fired internalelectrode layers, a base metal nickel is preferably used because of therelatively low price, etc. However, since nickel has a lower meltingpoint comparing with that of the dielectric powder included in thepre-fired dielectric layers, when firing the pre-fired dielectric layersand pre-fired internal electrode layers at a time, there arises adifference in sintering temperatures of the both. In the case where thesintering temperatures are largely different as such, when firing isperformed at a high temperature, nickel particles included in theconductive material become spheroidized due to grain growth and cavitiesarise at arbitrary places, consequently, it becomes difficult to formfired internal electrode layers in a continuous form. When firedinternal electrode layers are not in a continuous form as above,capacitance of the multilayer ceramic capacitor tends to decline.

To suppress grain growth of nickel particles at firing, a method ofadding dielectric particles together with the nickel particles to theconductive paste for internal electrode layers has been used. Here, thedielectric particles are added to be a common material. When nickelparticles and dielectric particles are included in the conductive pasteas such, an adding amount of the dielectric particles with respect tothe nickel particles had to be relatively large as 5 wt % or larger or1.33 mol % or larger to suppress grain growth of the nickel particles.

However, it is generally difficult to disperse dielectric particles andnickel particles uniformly, and the dielectric particles or nickelparticles tend to aggregate. Furthermore, aggregated dielectricparticles as such grow to be several μm or so by sintering to causebreaking of internal electrode layers. Therefore, there arises adisadvantage that the capacitance declines in any case.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electronic device,such as a multilayer ceramic capacitor, capable of suppressing graingrowth of conductive particles in a firing stage, effectively preventingspheroidizing of internal electrode layers and breaking of electrodesand effectively suppressing a decline of capacitance, particularly, evenwhen a thickness of the internal electrode layers is made thinner; and aproduction method thereof.

The present inventors found that, in the production method of anelectronic device, such as a multilayer ceramic capacitor, havinginternal electrode layers and dielectric layers, the above object can beattained by forming a pre-fired internal electrode thin film including aconductive component and a dielectric component, wherein a content ofthe dielectric component is larger than 0 mol % but not larger than 0.8mol % or larger than 0 wt % but not larger than 3 wt %, and firing amultilayer body of the pre-fired internal electrode thin films and greensheets; and completed the present invention.

Namely, according to a first aspect of the present invention, there isprovided a production method of an electronic device for producing anelectronic device including internal electrode layers and dielectriclayers, comprising the steps of:

forming a pre-fired internal electrode thin film including a conductivecomponent and a dielectric component;

stacking a green sheet to be a dielectric layer after firing and thepre-fired internal electrode thin film; and

firing a multilayer body of the green sheet and the pre-fired internalelectrode thin film;

wherein a content of the dielectric component in the pre-fired internalelectrode thin film is larger than 0 mol % but not larger than 0.8 mol %with respect to the entire pre-fired internal electrode thin film.

According to the first aspect of the present invention, there isprovided a production method of a multilayer ceramic capacitor forproducing a multilayer ceramic capacitor having an element body, whereininternal electrode layers and dielectric layers are alternately stacked,comprising the steps of:

forming a pre-fired internal electrode thin film including a conductivecomponent and a dielectric component;

alternately stacking green sheets to be dielectric layers after firingand the pre-fired internal electrode thin films; and

firing a multilayer body of the green sheets and the pre-fired internalelectrode thin films;

wherein a content of the dielectric component in the pre-fired internalelectrode thin film is larger than 0 mol % but not larger than 0.8 mol %with respect to the entire pre-fired internal electrode thin film.

Note that in the first aspect of the present invention, the dielectriccomponent in the pre-fired internal electrode thin film is notparticularly limited and BaTiO₃, Y₂O₃ and HfO₂, etc. may be mentioned.

According to a second aspect of the present invention, there is provideda production method of an electronic device for producing an electronicdevice including internal electrode layers and dielectric layers,comprising the steps of:

forming a pre-fired internal electrode thin film including a conductivecomponent and a dielectric component;

stacking a green sheet to be a dielectric layer after firing and thepre-fired internal electrode thin film; and

firing a multilayer body of the green sheet and the pre-fired internalelectrode thin film;

wherein a content of the dielectric component in the pre-fired internalelectrode thin film is larger than 0 wt % but not larger than 3 wt %with respect to the entire pre-fired internal electrode thin film.

Also, according to the first aspect of the present invention, there isprovided a production method of a multilayer ceramic capacitor forproducing a multilayer ceramic capacitor having an element body, whereininternal electrode layers and dielectric layers are alternately stacked,comprising the steps of:

forming a pre-fired internal electrode thin film including a conductivecomponent and a dielectric component;

alternately stacking green sheets to be dielectric layers after firingand the pre-fired internal electrode thin films; and

firing a multilayer body of the green sheets and the pre-fired internalelectrode thin films;

wherein a content of the dielectric component in the pre-fired internalelectrode thin film is larger than 0 wt % but not larger than 3 wt %with respect to the entire pre-fired internal electrode thin film.

Note that in the second aspect of the present invention, the dielectricthin film in the pre-fired internal electrode thin film is notparticularly limited and BaTiO₃, MgO, Al₂O₃, SiO₂, CaO, TiO₂, V₂O₃, MnO,SrO, Y₂O₃, ZrO₂, Nb₂O₅, BaO, HfO₂, La₂O₃, Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃,Er₂O₃, Tm₂O₃, Yb₂O₃, Lu₂O₃, CaTiO₃ and SrTiO₃, etc. may be mentioned.

In the present invention, a pre-fired internal electrode thin filmincluding a dielectric component together with a conductive component isformed as a pre-fired internal electrode thin film for composinginternal electrode layers after firing. Here, the dielectric componentis included as a common material. Therefore, spheroidizing in internalelectrode layers caused by a difference of sintering temperaturesbetween the dielectric material and the conductive material and breakingof electrodes, which have been notable disadvantages when the firedinternal electrode layers are made thinner, can be effectively preventedand a decline of the capacitance can be effectively suppressed.

In the present invention, the conductive component to be included in thepre-fired internal electrode thin film is not particularly limited asfar as it is composed of a material having conductivity and, forexample, metal materials, etc. may be mentioned. Also, the dielectriccomponent is not particularly limited and dielectric materials and othervariety of inorganic materials may be used.

Both of the conductive component and dielectric component to be includedin the internal electrode thin film form an internal electrode layerafter firing, but a part of the dielectric component may form adielectric layer after firing. Note that the pre-fired internalelectrode thin film may include other components than the conductivecomponent and dielectric component.

Also, in the present invention, by setting a content of the dielectriccomponent in the pre-fired internal electrode thin film to be largerthan 0 mol % but not larger than 0.8 mol % with respect to the entirepre-fired internal electrode thin film, breaking of electrodes can beeffectively prevented. Alternately, by setting a content of thedielectric component in the pre-fired internal electrode thin film to belarger than 0 wt % but not larger than 3 wt % with respect to the entirepre-fired internal electrode thin film, breaking of electrodes can beeffectively prevented.

The pre-fired internal electrode thin film can be formed by a method offorming a film directly on a green sheet to be a dielectric layer afterfiring and a method for forming a film on a release layer including adielectric material, etc.

In the production method of the present invention, it is preferable touse a transfer method of forming the pre-fired internal electrode thinfilm on the release layer, then, forming an adhesive layer on thepre-fired internal electrode thin film, and bonding the pre-firedinternal electrode thin film and a green sheet via the adhesive layer.

In the present invention, preferably, a thickness of the pre-firedinternal electronic thin film is 0.1 to 1.0 μm, and more preferably 0.1to 0.5. By setting a thickness of the pre-fired internal electrode thinfilm to be in the above ranges, the fired internal electrode layer canbe thinner.

In the present invention, the pre-fired internal electrode thin film ispreferably formed to be in a predetermined pattern by a thin filmformation method. Preferably, the thin film formation method is, forexample, the sputtering method, vapor deposition method or compositeplating method. The sputtering method is particularly preferable.

By forming a pre-fired internal electrode thin film comprising theconductive component and dielectric component by a thin film formationmethod, particularly by the sputtering method, the dielectric componentcan be uniformly distributed in the pre-fired internal electrode thinfilm. Particularly, in the present invention, preferably, the dielectriccomponent can be uniformly distributed at a nano-order level.Accordingly, even when a content of the dielectric component in thepre-fired internal electrode thin film is in a relatively small amountas above, the effect of adding the dielectric component can besufficiently brought out, and breaking of electrodes caused byspheroidizing of the conductive material, such as a metal material, canbe effectively prevented.

In the present invention, preferably, the pre-fired internal electrodethin film is formed by performing sputtering of a metal material and aninorganic material for composing the conductive component and thedielectric component at a time.

In the present invention, “performing sputtering at a time” means thatsputtering is performed by a method that the conductive component anddielectric component are uniformly distributed in the pre-fired internalelectrode thin film to be formed by the sputtering. As a method of“performing sputtering at a time”, for example, a method of alternatelysputtering a conductive target including a metal material and adielectric target including an inorganic material, such as a dielectricmaterial, alternately at predetermined time intervals (for example, 1 to30 seconds) may be mentioned. Alternately, a method of sputtering byusing a composite target including the conductive component and thedielectric component may be also preferably used.

Note that the inorganic material is not particularly limited and avariety of dielectric materials and variety of inorganic oxides, etc.may be mentioned. As inorganic oxides, for example, BaTiO₃, MgO, Al₂O₃,SiO₂, CaO, TiO₂, V₂O₃, MnO, SrO, Y₂O₃, ZrO₂, Nb₂O₅, BaO, HfO₂, La₂O₃,Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃, Er₂O₃, Tm₂O₃, Yb₂O₃, Lu₂O₃, CaTiO₃ andSrTiO₃, etc. may be mentioned, and they may be also included as additivesubcomponents in the pre-fired internal electrode thin film and thegreen sheet.

In the present invention, when performing sputtering as above, an inertgas is preferably used as an introduction gas. The inert gas is notparticularly limited, but an Ar gas is preferably used. Also, a gasintroduction pressure of the inert gas is preferably 0.01 to 2 Pa.

In the present invention, preferably, a dielectric component included inthe pre-fired internal electrode thin film and the green sheet includedielectric having substantially the same composition. Due to this,adhesiveness of the pre-fired internal electrode thin film and greensheet can be furthermore improved and the effects of the presentinvention are enhanced. Note that, in the present invention, thedielectric to be included in the dielectric thin film and that in thegreen sheet are not always required to have the completely samecomposition and it is sufficient if the compositions are substantiallythe same. Also, the pre-fired internal electrode thin film and/or thegreen sheet may be respectively added with different subcomponents inaccordance with need.

In the present invention, an average particle diameter of the dielectriccomponent included in the pre-fired internal electrode thin film ispreferably 1 to 10 nm. An average particle diameter of the dielectriccomponent can be measured by cutting the pre-fired internal electrodethin film 12 a and observing the cut surface by a TEM.

As a dielectric component included in the pre-fired internal electrodethin film and the dielectric to be included in the green sheet, forexample, calcium titanate, strontium titanate and barium titanate, etc.may be mentioned. Among them, barium titanate is preferably used.

In the present invention, preferably, the conductive component includedin the pre-fired internal electrode thin film includes nickel and/or anickel alloy as its main component. As the nickel alloy, an alloy of atleast one kind of element selected from ruthenium (Ru), rhodium (Rh),rhenium (Re) and platinum (Pt) with nickel is preferable, and a nickelcontent in the alloys is preferably 87 mol % or larger.

In the present invention, preferably, the multilayer body is fired in anatmosphere having an oxygen partial pressure of 10⁻² to 10⁻² Pa at atemperature of 1000° C. to 1300° C. According to the present invention,spheroidizing in the internal electrode layers and breaking ofelectrodes, which become notable disadvantages when firing at a highertemperature than a sintering temperature of the metal material, can beeffectively prevented, so that firing at the above temperature becomespossible.

Preferably, after firing the multilayer body, annealing is performed inan atmosphere having an oxygen partial pressure of 10⁻² to 100 Pa at atemperature of 1200° C. or lower. By performing annealing under aspecific condition after the firing, re-oxidization of the dielectriclayers is attained, the dielectric layers are prevented from becomingsemiconductor, and high insulation resistance can be obtained.

An electronic device according to the present invention is produced byany one of the methods explained above.

The electronic device is not particularly limited and a multilayerceramic capacitor, piezoelectric device, chip inductor, chip varistor,chip thermistor, chip resistor, and other surface mounted (SMD) chiptype electronic devices may be mentioned.

According to the present invention, it is possible to suppress graingrowth of conductive particles in the firing step, effectivelypreventing spheroidizing of fired internal electrode layers and breakingof electrodes, and effectively suppressing a decline of capacitance.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the attached drawings, in which:

FIG. 1 is a schematic sectional view of a multilayer ceramic capacitoraccording to an embodiment of the present invention;

FIG. 2 is a sectional view of a key part of a pre-fired internalelectrode thin film according to a production method of the presentinvention;

FIG. 3A is a sectional view of a key part showing a method of formingthe pre-fired internal electrode thin film of the present invention;

FIG. 3B is a sectional view of a key part showing a method of formingthe pre-fired internal electrode thin film of the present invention;

FIG. 3C is a sectional view of a key part showing a method of formingthe pre-fired internal electrode thin film of the present invention;

FIG. 4A is a schematic view from the side showing a sputtering methodaccording to an embodiment of the present invention;

FIG. 4B is a schematic view from the above showing a sputtering methodaccording to an embodiment of the present invention;

FIG. 5 is a sectional view of a key part of a sputtering targetaccording to an embodiment of the present invention

FIG. 6A is a sectional view of a key part showing a method oftransferring the pre-fired internal electrode thin film;

FIG. 6B is a sectional view of a key part showing a method oftransferring the pre-fired internal electrode thin film;

FIG. 6C is a sectional view of a key part showing a method oftransferring the pre-fired internal electrode thin film;

FIG. 7A is a sectional view of a key part showing a method oftransferring the pre-fired internal electrode thin film;

FIG. 7B is a sectional view of a key part showing a method oftransferring the pre-fired internal electrode thin film;

FIG. 7C is a sectional view of a key part showing a method oftransferring the pre-fired internal electrode thin film;

FIG. 8 is a sectional view of a key part of a multilayer body sampleaccording to an example of the present invention;

FIG. 9A is a SEM picture of an internal electrode layer after firingaccording to an example of the present invention; and

FIG. 9B is a SEM picture of an internal electrode layer after firingaccording to a comparative example of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Below, the present invention will be explained based on embodimentsshown in drawings.

First, as one embodiment of electronic devices produced by the method ofthe present invention, an overall configuration of a multilayer ceramiccapacitor will be explained.

AS shown in FIG. 1, a multilayer ceramic capacitor 2 according to thepresent embodiment comprises a capacitor element body 4, a firstterminal electrode 6 and a second terminal electrode 8. The capacitorelement body 4 comprises dielectric layers 10 and internal electrodelayers 12, and the internal electrode layers 12 are alternately stackedbetween the dielectric layers 10. The alternately stacked internalelectrode layers 12 on one side are electrically connected to inside ofthe first terminal electrode 6 formed outside of a first end portion 4 aof the capacitor element body 4. Also, the alternately stacked internalelectrode layers 12 on the other side are electrically connected toinside of the second terminal electrode 8 formed outside of a second endportion 4 b of the capacitor element body 4.

In the present embodiment, the internal electrode layer 12 is formed byfiring a pre-fired internal electrode thin film 12 a including aconductive component and a dielectric component shown in FIG. 2 as willbe explained later on.

A material of the dielectric layers 10 is not particularly limited andit may be composed of dielectric materials, such as calcium titanate,strontium titanate and barium titanate. Among them, barium titanate ispreferably used. Furthermore, the dielectric layers 10 may be added witha variety of subcomponents in accordance with need. A thickness of eachdielectric layer 10 is not particularly limited but is generally severalμm to hundreds of μm. Particularly in this embodiment, it is made asthin as preferably 5 μm or thinner, and more preferably 3 μm or thinner.

Also, a material of the terminal electrodes 6 and 8 is not particularlylimited and copper, copper alloys, nickel and nickel alloys, etc. arenormally used. Silver and an alloy of silver and palladium may be alsoused. A thickness of the terminal electrodes 6 and 8 is not particularlylimited and is normally 10 to 50 μm or so.

A shape and size of the multilayer ceramic capacitor 2 may be suitablydetermined in accordance with the use object. When the multilayerceramic capacitor 2 is a rectangular parallelepiped shape, it isnormally a length (0.6 to 5.6 mm, preferably 0.6 to 3.2 mm)×width (0.3to 5.0 mm, preferably 0.3 to 1.6 mm)×thickness (0.1 to 1.9 mm,preferably 0.3 to 1.6 mm) or so.

Next, an example of a production method of the multilayer ceramiccapacitor 2 according to the present embodiment will be explained.

First, dielectric paste is prepared for producing a ceramic green sheetfor composing the dielectric layers 10 shown in FIG. 1 after firing.

The dielectric paste is normally composed of organic solvent based pasteobtained by kneading a dielectric material and an organic vehicle orwater based paste.

The dielectric material may be suitably selected from composite oxidesand a variety of compounds, which become oxides by firing, for example,carbonates, nitrites, hydroxides and organic metal compounds, etc. andmixed for use. The dielectric material is normally used as a powderhaving an average particle diameter of 0.1 to 3.0 μm or so. Note that,to form an extremely thin green sheet, it is preferable to use a finerpowder than a thickness of the green sheet.

An organic vehicle is obtained by dissolving a binder in an organicsolvent. The binder to be used for the organic vehicle is notparticularly limited and may be suitably selected from a variety ofnormal binders, such as ethyl cellulose, polyvinyl butyral and anacrylic resin. Preferably, polyvinyl butyral or other butyral basedresin is used.

Also, the organic solvent to be used for the organic vehicle is notparticularly limited and an organic solvent, such as terpineol, butylcarbitol, acetone and toluene, is used. A vehicle in a water based pasteis obtained by dissolving a water-soluble binder in water. Thewater-soluble binder is not particularly limited and polyvinyl alcohol,methyl cellulose, hydroxyl ethyl cellulose, water-soluble acrylic resinand emulsion, etc. may be used. A content of each component in thedielectric paste is not particularly limited and may be a normalcontent, for example, about 1 to 5 wt % of a binder and about 10 to 50wt % of a solvent (or water).

The dielectric paste may contain additives selected from a variety ofdispersants, plasticizers, dielectrics, glass frits and insulators, etc.in accordance with need. Note that a total content of them is preferably10 wt % or smaller. When using a butyral based resin as the binderresin. It is preferable that a content of a plasticizer is 25 to 100parts by weight with respect to 100 parts by weight of the binder resin.When the plasticizer is too small, the green sheet tends to becomerattle, while when too large, the plasticizer exudes and thehandleability becomes poor.

Next, by using the dielectric paste, a green sheet 10 a is formed to bea thickness of preferably 0.5 to 30 μm and more preferably 0.5 to 10 μmor so on a carrier sheet 30 as a second support sheet as shown in FIG.7A by the doctor blade method, etc. A temperature of drying the greensheet 10 a is preferably 50 to 100° C. and the drying time is preferably1 to 5 minutes.

Next, as shown in FIG. 6A, a carrier sheet 20 as a first support sheetis prepared separately from the carrier sheet 30, and a release layer 22is formed thereon. Then, on a surface of the release layer 22, apre-fired internal electrode thin film 12 a for composing an internalelectrode layer 12 after firing is formed in a predetermined pattern.

For example, a PET film, etc. is used as the carrier sheets 20 and 30and those coated with silicon, etc. are preferable to improve thereleasing capability. Thicknesses of the carrier sheets 20 and 30 arenot particularly limited, but 5 to 100 μm is preferable. The thicknessesof the carrier sheets 20 and 30 may be same or different.

The release layer 22 includes the same dielectric particles as thedielectric composing the green sheet 10 a shown in FIG. 7A. Also, therelease layer 22 includes a binder, a plasticizer and a releasing agentas an optional component in addition to the dielectric particles. Aparticle diameter of the dielectric particles may be the same as aparticle diameter of the dielectric particles included in the greensheet, but it is preferably smaller. A method of forming the releaselayer 22 is not particularly limited but a method of applying by using awire bar coater or a die coater is preferable because it has to beformed to be extremely thin.

The pre-fired internal electrode thin film 12 a is formed on the releaselayer 22 as shown in FIG. 2 and includes a conductive component and adielectric component.

The conductive component to be included in the internal electrode thinfilm 12 a is not particularly limited as far as it is composed of amaterial having conductivity and metal materials, etc. may be mentioned.As such metal materials, for example when using a material havingreduction resistance as a component of the dielectric layer 10, basemetals may be used. As the base metals, metals including nickel as themain component or alloys of nickel with other metals are preferable. Asnickel alloys, alloys of at least one kind of element selected fromruthenium (Ru), rhodium (Rh), rhenium (Re) and platinum (Pt) with nickelare preferable, and a nickel content in the alloys is preferably 87 mol% or larger. Note that the nickel alloys may include a variety of tracecomponents, such as S, C and P, in an amount of about 0.1 wt % orsmaller.

A dielectric component to be included in the internal electrode thinfilm 12 a is not particularly limited and a variety of inorganicmaterials, such as a dielectric material, may be used. But it ispreferable to include a dielectric material having substantially thesame composition as that of the dielectric material included in therelease layer 22 and the green sheet 10 a. As a result, adhesiveness ofcontact surfaces formed between the internal electrode thin film 12 a,the release layer 22 and the green sheet 10 a can be furthermoreimproved.

A content of the dielectric component in the internal electrode thinfilm 12 a is set to be larger than 0 mol % but not larger than 0.8 mol %with respect to the entire internal electrode thin film. Alternately,the content of the dielectric component in the internal electrode thinfilm 12 a is set to be larger than 0 wt % but not larger than 3 wt %with respect to the entire internal electrode thin film. In the presentembodiment, while it will be explained later on, the internal electrodethin film 12 a is formed by a thin film formation method, such as thesputtering method, so that the dielectric component can be uniformlydispersed at a nano-order level. Accordingly, even when a content of thedielectric component is in a relatively small amount, the effect ofadding the dielectric component can be efficiently brought out, andbreaking of electrodes caused by spheroidizing of the conductivematerial, such as a metal material, can be effectively prevented.

A thickness of the pre-fixed internal electrode thin film 12 a ispreferably 0.1 to 1.0 μm, and more preferably 0.1 to 0.5 μm. By settingthe thickness of the internal electrode thin film 12 a to be in theabove ranges, the fired internal electrode layer can become thinner.

As a method of forming the internal electrode thin film 12 a including aconductive component and a dielectric component, the plating method,vapor deposition method, sputtering method and other thin film formationmethods may be mentioned. In the present embodiment, it is formed by thesputtering method.

When forming the pre-fired internal electrode thin film 12 a by thesputtering method, it is performed, for example, as below.

First, as shown in FIG. 3A, on a surface of the release layer 22 on thecarrier sheet 20, a metal mask 44 having a predetermined pattern isformed as a shield mask. Next, as shown in FIG. 3B, an internalelectrode thin film 12 a is formed on the release layer 22.

In the present embodiment, the internal electrode thin film 12 a isformed by using a conductive target 40 including a conductive componentand a dielectric target 42 including a dielectric component as shown inFIG. 4A and FIG. 4B and performing sputtering alternately by both of thetargets. Namely, in the present embodiment, as shown in FIG. 4A and FIG.4B, the carrier sheet 20 formed with the release layer 22 and the metalmask 44 (not shown) rotates above the conductive target and thedielectric target 42 so as to form a conductive component and dielectriccomponent on the release layer 22 alternately at predetermined timeintervals (for example, 1 to 30 seconds). By forming the conductivecomponent and dielectric component alternately at intervals of severalseconds, the dielectric component can be uniformly distributed in theinternal electrode thin film 12 a at a nano-order level, and aggregationof the dielectric component can be effectively prevented.

Namely, in the present embodiment, an average particle diameter of thedielectric component included in the pre-fired internal electrode thinfilm 12 a can be preferably 1 to 10 nm and uniform dispersion can beattained. Note that the average particle diameter of the dielectriccomponent can be measured by cutting the pre-fired internal electrodethin film 12 a and observing the cut surface by a TEM.

The rotation rate is, for example, 0.5 to 15 rpm, and sputtering of theconductive target 40 and the dielectric target 42 is preferablyperformed at intervals of 1 to 30 seconds.

As the conductive target 40 to from the conductive component in theinternal electrode thin film 12 a, a conductive material may be usedand, for example, metals including nickel as the main component oralloys of nickel with other metals, etc. may be used.

Also, as the dielectric target 42 for forming the dielectric componentin the internal electrode thin film 12 a, dielectric materials and othervariety of inorganic materials may be used and, for example, compositeoxides and a variety of compounds which become oxides by firing, etc.may be mentioned.

When performing sputtering, it is preferable to use an inert gas,particularly, an Ar gas as an introduction gas, and the gas introductionpressure is preferably 0.1 to 2 Pa. As other sputtering conditions, theultimate vacuum is preferably 10⁻² Pa and lower preferably 10⁻³ Pa orlower, and the sputtering temperature is preferably 20 to 150° C. andmore preferably 20 to 150° C.

Note that, in the present embodiment, a content ratio of the conductivecomponent and the dielectric component in the internal electrode thinfilm 12 a can be controlled, for example, by adjusting outputs of theconductive target 40 and the dielectric target 42. An output of theconductive target 40 is preferably 50 to 400 W and more preferably 100to 300 W, and an output of the dielectric target 42 is preferably 10 to100 W and more preferably 10 to 50 W. Also, preferably, a film formingrate of the conductive component is 5 to 20 nm/min., and a film formingrate of the dielectric component is 1 nm/min. or lower.

A thickness of the internal electrode thin film 12 a can be controlledby adjusting the respective sputtering conditions and film forming time.

Next, by removing the metal mask 44, the internal electrode thin film 12a having a predetermined pattern as shown in FIG. 3C and including aconductive component and a dielectric component can be formed on asurface of the release layer 22.

Next, separately from the carrier sheets 20 and 30, as shown in FIG. 6A,an adhesive layer transfer sheet is prepared, wherein an adhesive layer28 is formed on a surface of a carrier sheet 26 as the third supportsheet. The carrier sheet 26 is the same sheet as the carrier sheets 20and 30. A composition of the adhesive layer 28 is the same as that ofthe release layer 22 except for not including any mold releasing agents.Namely, the adhesive layer 28 includes a binder, plasticizer and moldreleasing agent. The adhesive layer 28 may include the same dielectricparticles as those in the dielectric composing the green sheet 10 a, butwhen forming a thin adhesive layer having a thinner thickness than aparticle diameter of the dielectric particles, it is more preferable notto include the dielectric particles.

Next, the adhesive layer is formed on a surface of the internalelectrode thin film 12 a shown in FIG. 6A by a transfer method. Namely,as shown in FIG. 6B, the adhesive layer 28 of the carrier sheet 26 ispressed against the surface of the internal electrode layer 12 a, heatand pressure are applied thereto, then, the carrier sheet 26 is removed,consequently, the adhesive layer 28 is transferred to the surface of theinternal electrode thin film 12 a as shown in FIG. 6C.

A heating temperature at that time is preferably 40 to 100° C., and thepressure force is preferably 0.2 to 15 MPa. The pressure may be appliedby a press or by a calendar roll, but it is preferable to use a pair ofrolls.

After that, the internal electrode thin film 12 a is bonded with thesurface of the green sheet 10 a formed on the surface of the carriersheet 30 shown in FIG. 7A. For that purpose, as shown in FIG. 7B, theinternal electrode thin film 12 a on the carrier sheet 20 is pressedagainst the surface of the green sheet 10 a together with the carriersheet 20 via the adhesive layer 28, heat and pressure are applied so asto transfer the internal electrode thin film 12 a to the surface of thegreen sheet 10 a as shown in FIG. 7C. Note that since the carrier sheet30 on the green sheet side is peeled off, when seeing from the greensheet 10 a side, the green sheet 10 a is transferred to the internalelectrode thin film 12 a via the adhesive layer 28.

The heat and pressure at the transfer may be applied by a press or by acalendar roll, but it is preferable to use a pair of rolls. The heatingtemperature and pressure are the same as those in transferring theadhesive layer 28.

From the steps as above shown in FIG. 6A to FIG. 7C, the pre-firedinternal electrode thin film 12 a including a conductive component and adielectric component is formed on one green sheet 10 a. By using theresult, a multilayer body, wherein a large number of the internalelectrode thin films 12 a and the green sheets 10 a are alternatelystacked, is obtained.

Then, after finally pressuring the multilayer body, the carrier sheet 20is peeled off. A pressure at the final pressuring is preferably 10 to200 MPa. Also, the heating temperature is preferably 40 to 100° C. Afterthat, the multilayer body is cut to be a predetermine size to form agreen chip. Then, the green chip is subjected to binder removalprocessing and firing.

The binder removal processing is preferably performed in the air or inN₂ of a binder removal atmosphere when nickel as a base metal is used asthe conductive component of the internal electrode layer as in thepresent invention. Also, as other binder removal conditions, thetemperature raising rate is preferably 5 to 300° C./hour and morepreferably 10 to 50° C./hour, the holding temperature is preferably 200to 400° C. and more preferably 250 to 350° C., and the temperatureholding time is preferably 0.5 to 20 hours and more preferably 1 to 10hours.

Firing of the green chip is preferably performed in an atmosphere underan oxygen partial pressure of 10⁻¹⁰ to 10⁻² Pa and more preferably 10⁻¹⁰to 10⁻⁵ Pa. When the oxygen partial pressure at the firing is too low,the conductive material in the internal electrode layer may result inabnormal sintering to be broken, while when too high, the internalelectrode layer tends to be oxidized.

Firing of the green chip is performed at a low temperature of 1300° C.or lower, more preferably 1000 to 1300° C., and particularly preferably1150 to 1250° C. When the firing temperature is too low, the green chipis not densified, while when too high, breaking of electrodes in theinternal electrode layer is caused and the dielectric is reduced.

As other firing conditions, the temperature raising rate is preferably50 to 500° C./hour and more preferably 200 to 300° C./hour, thetemperature holding time is preferably 0.5 to 8 hours and morepreferably 1 to 3 hours, and the cooling rate is preferably 50 to 500°C./hour and more preferably 200 to 300° C./hour. The firing atmosphereis preferably a reducing atmosphere, and a mixed gas of N₂ and H₂ in awet state is preferably used as the atmosphere gas.

Next, annealing is performed on the fired capacitor chip body. Annealingis processing for re-oxidizing the dielectric layers, and an acceleratedlifetime of insulation resistance (IR) can be remarkably elongated andreliability improves by that.

Annealing of the fired capacitor chip body is preferably performed undera higher oxygen partial pressure than that of the reducing atmosphere atthe time of firing, specifically, the oxygen partial pressure of theatmosphere is preferably 10⁻² to 100 Pa, and more preferably 10⁻² to 10Pa. When the oxygen partial pressure at annealing is too low,re-oxidizing of the dielectric layers 10 becomes difficult, while whentoo high, the internal electrode layers 12 tend to be oxidized.

In the present embodiment, the holding temperature or the highesttemperature at annealing is preferably 1200° C. or lower, morepreferably 900 to 1150° C., and particularly preferably 1000 to 1100° C.Also, in the present invention, the holding time of the temperature ispreferably 0.5 to 4 hours and more preferably 1 to 3 hours. When theholding temperature or the highest temperature at annealing is lowerthan the above ranges, oxidization of the dielectric material becomesinsufficient and the insulation resistance lifetime tends to becomeshort, while when it is higher than the above ranges, it is liable thatnickel in the internal electrode layers is oxidized and not onlydeclining the capacity but it reacts with the dielectric base and thelifetime also becomes short. Note that the annealing may be composedonly of the temperature raising step and the temperature lowering step.Namely, the temperature holding time may be zero. In that case, theholding temperature is the highest temperature.

As other annealing conditions, the cooling rate is preferably 50 to 500°C./hour and more preferably 100 to 300° C./hour. As the atmosphere gasat annealing, for example, a wet N₂ gas, etc. is preferably used.

Note that to wet the N₂ gas, for example, a wetter, etc. is used. Inthat case, the water temperature is preferably 0 to 75° C. or so.

The binder removal processing, firing and annealing may be performedcontinuously or separately. When performing continuously, the atmosphereis changed without cooling after the binder removal processing,continuously, the temperature is raised to the holding temperature atfiring to perform firing. Next, it is cooled and the annealing ispreferably performed by changing the atmosphere when the temperaturereaches to the holding temperature of the annealing. On the other hand,when performing them separately, at the time of firing, after raisingthe temperature to the holding temperature of the binder removalprocessing in an atmosphere of a nitrogen gas or a wet nitrogen gas, theatmosphere is changed, and the temperature is preferably furthermoreraised. After that, after cooling the temperature to the holdingtemperature of the annealing, it is preferable that the coolingcontinues by changing the atmosphere again to a N₂ gas or a wet N₂ gas.Also, in the annealing, after raising the temperature to the holdingtemperature under the N₂ gas atmosphere, the atmosphere may be changed,or the entire process of the annealing may be in a wet N₂ gasatmosphere.

End surface polishing, for example, by barrel polishing or sand blast,etc. is performed on the sintered body (element body 4) obtained asabove, and the external electrode paste is burnt to form externalelectrodes 6 and 8. A firing condition of the external electrode pasteis preferably, for example, at 600 to 800° C. in a wet mixed gas of N₂and H₂ for 10 minutes to 1 hour or so. A pad layer is formed by plating,etc. on the surface of the external electrodes 6 and 8 if necessary.Note that the terminal electrode paste may be fabricated in the same wayas the electrode paste explained above.

A multilayer ceramic capacitor of the present invention produced asabove is mounted on a print substrate, etc. by soldering, etc. and usedfor a variety of electronic apparatuses, etc.

In the present embodiment, an internal electrode thin film 12 aincluding a conductive component and a dielectric component, wherein acontent of the dielectric component is larger than 0 mol % but notlarger than 0.8 mol %, is formed as the pre-fired internal electrodethin film 12 a for composing the internal electrode layer 12 afterfiring. Alternately, an internal electrode thin film 12 a including aconductive component and a dielectric component, wherein a content ofthe dielectric component is larger than 0 wt % but not larger than 3 wt%, is formed as the pre-fired internal electrode thin film 12 a forcomposing the internal electrode layer 12 after firing. Therefore,spheroidizing of the internal electrode layers and breaking ofelectrodes caused by a difference of sintering temperatures between thedielectric material and conductive material in the case of making thefired internal electrode layers 12 thinner, which have been notabledisadvantages, are effectively prevented and a decline of thecapacitance can be effectively suppressed.

Also, in the present embodiment, the internal electrode thin film 12 aincluding a conductive component and a dielectric component is formed bythe sputtering method, so that the dielectric component can be uniformlydistributed in the internal electrode thin film 12 a at a nano-orderlevel. Accordingly, even when a content of the dielectric component inthe internal electrode thin film 12 a is in a relatively small amount asexplained above, the effect of adding the dielectric component can besufficiently brought out, and breaking of electrodes caused byspheroidizing of the conductive material, such as a metal material, canbe effectively prevented.

An embodiment of the present invention was explained above, however, thepresent invention is not limited to the embodiment and a variety ofmodifications may be naturally made within the scope of the presentinvention.

For example, in the above embodiment, a multilayer ceramic capacitor wasexplained as an example of an electronic device according to the presentinvention, however, the electronic device according to the presentinvention is not limited to multilayer ceramic capacitors and thepresent invention can be applied to other electronic devices.

Also, in the above embodiment, the conductive target 40 and thedielectric target 42 as shown in FIG. 4A and FIG. 4B were used assputtering targets at the time of forming the pre-fired internalelectrode thin film 12 a by the sputtering method, however, compositetargets obtained by mixing and firing a conductive component anddielectric component may be also used. When using such compositetargets, a rate of the conductive component and the dielectric componentincluded in the internal electrode thin film 12 a can be controlled byadjusting a mixing ratio of the conductive component and the dielectriccomponent in the composite targets.

Alternately, as the sputtering targets, a target formed by mounting aplurality of dielectric targets processed to be in a pellet shape on aconductive target as shown in FIG. 5 may be also used. In that case,also, by adjusting a size or number of the pellet-shaped dielectrictarget to be mounted on the conductive target, the ratio of theconductive component and dielectric component to be included in theinternal electrode thin film 12 a can be controlled.

Also, before the step of forming the adhesive layer 28 on the surface ofthe pre-fired internal electrode thin film 12 a, a blank pattern layerhaving substantially the same thickness as that of the internalelectrode thin film 12 a and composed of substantially the same materialas the green sheet 10 a may be formed on the surface of the releaselayer 22, on which the internal electrode thin film 12 a is not formed.

Also, in the present invention, other thin film formation methods thanthe sputtering method may be used. As other thin film formation methods,the vapor deposition method and composite plating method, etc. may bementioned.

EXAMPLES

Below, the present invention will be explained based on furthermoredetailed examples, but the present invention is not limited to theseexamples.

Example 1 Production of Respective Paste

First, a BaTiO₃ powder (BT-02 made by Sakai Chemical Industry Co.,Ltd.), MgCO₃, MnCO₃, (Ba_(0.6)Ca_(0.4))SiO₃ and a powder selected fromrare earths (Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃, Er₂O₃, Tm₂O₃, Yb₂O₃, Lu₂O₃ andY₂O₃) were wet mixed by a ball mill for 16 hours and dried to obtain adielectric material. An average particle diameter of these materialpowders was 0.1 to 1 μm. The (Ba_(0.6)Ca_(0.4))SiO₃ was produced by wetmixing BaCo₃, CaCO₃ and SiO₂ by a ball mill for 16 hours, drying, then,firing at 1150° C. in the air, and dry pulverizing the result by a ballmill for 100 hours.

To make the obtained dielectric material to be paste, an organic vehiclewas added to the dielectric material and mixed by a ball mill, so thatdielectric green sheet paste was obtained. The organic vehicle has acompounding ratio of polyvinyl butyral as a binder in an amount of 6parts by weight, bis(2-ethylhexyl)phthalate (DOP) as a plasticizer in anamount of 3 parts by weight, ethyl acetate in an amount of 55 parts byweight, toluene in an amount of 10 parts by weight and paraffin as areleasing agent in an amount of 0.5 part by weight with respect to 100parts by weight of the dielectric material.

Next, the dielectric green sheet paste was diluted two times in a weightratio with ethanol/toluene (55/10) to obtain release layer paste.

Then, the same dielectric green sheet paste except for not includingdielectric particles and releasing agent was diluted four times in aweight ratio with toluene to obtain adhesive layer paste.

Formation of Green Sheet 10 a

First, the dielectric green sheet paste was applied to a PET film(second support sheet) by using a wire bar coater and, then, dried toform a green sheet having a thickness of 1.0 μm.

Formation of Pre-Fired Internal Electrode Thin Film 12 a

The release layer paste is applied on another PET film (first supportsheet) by using a wire bar coater and, then, dried to form a releaselayer having a thickness of 0.3 μm.

Next, on a surface of the release layer, the pre-fired internalelectrode thin film 12 a including a conductive component and adielectric component as shown in FIG. 2 was formed by the sputteringmethod by using a metal mask 44 having a predetermined pattern forforming an internal electrode thin film 12 a. A thickness of theinternal electrode thin film 12 a was 0.4 μm, and a content ratio of theconductive component and dielectric component to be included in theinternal electrode thin film 12 a was as those shown in Table 1,respectively. Note that the content ratio of the dielectric componentand the dielectric component was adjusted by changing an output of thedielectric target while keeping an output of the conductive targetconstant.

In this example, sputtering was performed by the method shown in FIG. 4Aand FIG. 4B by first preparing a conductive target for forming aconductive component and a dielectric target for forming a dielectriccomponent. Ni was used as the conductive target, and BaTiO₃ was used asthe dielectric target. Sputtering targets obtained by cutting into ashape having a diameter of about 4 inches and a thickness of 3 mm wereused as the Ni and BaTiO₃ targets.

As other sputtering conditions, the ultimate vacuum was 10⁻³ or lower,an Ar gas introduction pressure was 0.5 Pa, and the temperature was theroom temperature (20° C.). Also, outputs at sputtering was 200 W at theNi target and 10 to 100 W at the BaTiO₃ target.

Note that, in this example, when forming the internal electrode thinfilm 12 a on respective samples, a film was also formed on a glasssubstrate by sputtering at the same time. Then, the glass substratehaving a thin film formed thereon was broken and the broken sectionsurface was observed by SEM so as to measure a thickness of the internalelectrode thin film 12 a formed by sputtering.

Formation of Adhesive Layer

The adhesive layer paste explained above was applied to another PET film(third support sheet) by using a wire bar coater and, then, dried toform an adhesive layer having a thickness of 0.2 μm. Note that, in thisexample, a PET film having surfaces subjected to release processing by asilicon based resin was used for all of the PET films (the first supportsheet, second support sheet and third support sheet).

Formation of Final Multilayer Body (Pre-Fired Element Body)

First, the adhesive layer 28 was transferred to a surface of theinternal electrode thin film 12 a by the method shown in FIG. 6. Attransferring, a pair of rolls were used, the pressure was 1 MPa and thetemperature was 80° C.

Next, the internal electrode thin film 12 a was bonded (transferred) toa surface of the green sheet 10 a via the adhesive layer 28 by themethod shown in FIG. 7. At transferring, a pair of rolls were used, thepressure was 1 MPa and the temperature was 80° C.

Next, the internal electrode thin films 12 a and green sheets 10 a werestacked successively and, finally, a final multilayer body was obtained,wherein 21 layers of internal electrode thin films 12 a were stacked. Astacking condition was a pressure of 50 MPa and a temperature of 120° C.

Production of Sintered Body

Next, the final multilayer body was cut to be a predetermined size andsubjected to binder removal processing, firing and annealing (thermaltreatment), so that a sintered body in a chip shape was produced.

The binder removal processing was performed as below.

Temperature raising rate: 15 to 50° C./hour

Holding temperature: 400° C.

Holding time: 2 hours

Cooling rate: 300° C./hour

Atmosphere gas: wet N₂ gas

The firing was performed as below.

Temperature raising rate: 200 to 300° C./hour

Holding temperature: 1200° C.

Holding time: 2 hours

Cooling rate: 300° C./hour

Atmosphere gas: wet mixed gas of N₂+H₂

Oxygen partial pressure: 10⁻⁷ Pa

The annealing (re-oxidization) was performed as below.

Temperature raising rate: 200 to 300° C./hour

Holding temperature: 1050° C.

Temperature holding time: 2 hours

Cooling rate: 300° C./hour

Atmosphere gas: wet N₂ gas

Oxygen partial pressure: 10⁻¹ Pa

Note that a wetter with a water temperature of 0 to 75° C. was used towet the atmosphere gases at the time of binder removal, firing andannealing.

Next, end surfaces of the chip-shaped sintered body was polished by sandblast, then, an external electrode paste was transferred to the endsurfaces and fired at 800° C. for 10 minutes in a wet N₂+H₂ atmosphereto form external electrodes, so that a multilayer capacitor samplehaving the configuration shown in FIG. 1 was obtained.

A size of each of the thus obtained samples was 3.2 mm×1.6 mm×0.6 mm,the number of dielectric layers sandwiched by the internal electrodelayers was 21, a thickness thereof was 1 μm, and a thickness of theinternal electrode layer was 0.5 μm. Electric characteristics(capacitance C and dielectric loss tan δ) were evaluated on each sample.The results are shown in Table 1. The electric characteristics(capacitance C and dielectric loss tan δ) were evaluated as below.

The capacitance C (unit: μF) was measured by a digital LCR meter (4274Amade by YHP) at a reference temperature of 25° C. under conditions thata frequency was 1 kHz and an input signal level (measurement voltage)was 1 Vrms. Capacitance C of 0.9 μF or higher was evaluated good.

The dielectric loss tan δ was measured by using a digital LCR meter(4274A made by YHP) at a reference temperature of 25° C. underconditions that a frequency was 1 kHz and an input signal level(measurement voltage) was 1 Vrms. Dielectric loss tan δ of less than 0.1was evaluated good.

Note that the characteristic values were obtained from an average valueof values measured by using the number of samples n=10. In Table 1, “o”in the evaluation standard column indicates that preferable results wereexhibited in all of the above characteristics, and “x” indicates thatone or more results were not preferable among those.

TABLE 1 Pre-Fired Internal Electrode Thin Film 12a Content Ratio ContentRatio Sample Thickness of Nickel of BaTiO₃ Capacitance No. [μm] [mol %][mol %] [μF] tan δ Evaluation 1 Comparative 0.4 100 0.0 0.83 0.01 XExample 2 Example 0.4 99.82 0.18 0.98 0.01 ◯ 3 Example 0.4 99.65 0.351.1 0.01 ◯ 4 Example 0.4 99.20 0.80 0.95 0.02 ◯ 5 Comparative 0.4 98.671.33 0.72 0.02 X Example

Table 1 shows a thickness of a pre-fired internal electrode thin film 12a formed for each sample, a content ratio of nickel and BaTiO₃,capacitance, dielectric loss tan δ and evaluation on each sample.

As shown in Table 1, all of the samples 2 to 4 in the example, whereinthe pre-fired internal electrode thin film 12 a included nickel as aconductive component and BaTiO₃ as a dielectric component and a contentratio of BaTiO₃ was respectively 0.18, 0.35 and 0.80 mol %, exhibitedpreferable results that the capacitance exceeded 0.9 μF and thedielectric loss tan δ was less than 0.1.

On the other hand, in the sample 1 as a comparative example, whereinBaTiO₃ as a dielectric component was not included in the internalelectrode thin film 12 a, spheroidizing arose in the internal electrodelayers, breaking of electrodes arose and the capacitance became as lowas 0.83 μF. Also, in a sample as a comparative example, wherein acontent ratio of BaTiO₃ in the internal electrode thin film 12 a was1.33 mol %, breaking of the internal electrode layers arose and thecapacitance became low as 0.72 μF.

It was confirmed that as a result that a conductive component and adielectric component were included in the pre-fired internal electrodethin film and a content of the dielectric component in the internalelectrode thin film was larger than 0 mol % but not larger than 0.8 mol% with respect to the entire internal electrode thin film, spheroidizingin the internal electrode layers and breaking of electrodes could beprevented effectively and a decline of the capacitance could besuppressed even when the fired internal electrode layers were madethinner.

Example 2

The dielectric green sheet paste produced in the example 1 was appliedto the PET film (carrier sheet) by using a wire bar coater and, then,dried to obtain a green sheet 10 a. A pre-fired internal electrode thinfilm 12 a was formed on the green sheet 10 a in the same way as in theexample 1 and a multilayer body as shown in FIG. 8 was produced. Next,the PET film was removed from the multilayer body to produce a pre-firedsample composed of the green sheet 10 a and the internal electrode thinfilm 12 a. The pre-fired sample was subjected to binder removal, firingand annealing in the same way as in the example 1, so that a sample forsurface observation after firing composed of the dielectric layers 10and the internal electrode layers 12 was produced.

Next, SEM observation was made on the obtained surface observationsample from the vertical direction with respect to the surface formedwith the internal electrode layer 12, and the fired internal electrodelayer was observed and evaluated. Obtained SEM pictures are shown inFIG. 9A and FIG. 9B. FIG. 9A corresponds to the sample 3 in the example1, and FIG. 9B corresponds to the sample 1 in the example 1. Namely,FIG. 9A and FIG. 9B are SEM pictures of samples, wherein internalelectrode thin film was formed under the same condition as that in therespective capacitor samples in the example 1.

FIG. 9A is a SEM picture of a sample, wherein the pre-fired internalelectrode thin film 12 a included nickel as a conductive component andBaTiO₃ as a dielectric component and a content ratio of BaTiO₃ was 0.35mol %, and as is obvious from the picture, breaking of the internalelectrode layers (white parts in the SEM picture) was not observed and apreferable result was obtained.

On the other hand, from FIG. 9B, the sample, wherein BaTiO₃ as adielectric component was not included in the internal electrode thinfilm 12 a, exhibited results that spheroidizing of nickel arose andbreaking of electrodes became notable. Particularly, by comparing FIG.9A and FIG. 9B, it can be confirmed that spheroidizing of nickel can besuppressed and breaking of internal electrodes can be effectivelyprevented as a result that the internal electrode thin film 12 aincludes a dielectric component in a range of the present invention.

Example 3

Other than using Yb₂O₃ instead of BaTiO₃ as a dielectric target whenforming the pre-fired internal electrode thin film 12 a, samples wereobtained in the same way as in the example 1. An evaluation of electriccharacteristics (capacitance C and dielectric loss tan δ) was made oneach sample. The results are shown in Table 2. The electriccharacteristics (capacitance C and dielectric loss tan δ) were evaluatedin the same way as in the example 1.

TABLE 2 Pre-Fired Internal Electrode Thin Film 12a Content Ratio ContentRatio Sample Thickness of Nickel of BaTiO₃ Capacitance No. [μm] [mol %][mol %] [μF] tan δ Evaluation 6 Comparative 0.4 100.00 0.0 0.83 0.01 XExample 7 Example 0.4 99.30 0.70 0.97 0.02 ◯ 8 Example 0.4 98.10 1.900.95 0.02 ◯ 9 Example 0.4 97.00 3.00 0.92 0.02 ◯ 10 Comparative 0.494.86 5.14 0.74 0.02 X Example

Table 2 shows a thickness of a pre-fired internal electrode thin film 12a formed for each sample, a content ratio of nickel and Yb₂O₃,capacitance, dielectric loss tan δ and evaluation on each sample.

As shown in Table 2, all of the samples 2 to 4 in the example, whereinthe pre-fired internal electrode thin film 12 a included nickel as aconductive component and Yb₂O₃ as a dielectric component and a contentratio of Yb₂O₃ was respectively 0.7, 1.9 and 3 wt %, exhibitedpreferable results that the capacitance exceeded 0.9 μF and thedielectric loss tan δ became less than 0.1.

On the other hand, in the sample 1 as a comparative example, whereinYb₂O₃ as a dielectric component was not included in the internalelectrode thin film 12 a, spheroidizing arose in the internal electrodelayers, breaking of electrodes arose and the capacitance became as lowas 0.83 μF. Also, in the sample as a comparative example, wherein acontent ratio of Yb₂O₃ in the internal electrode thin film 12 a was 5.14wt %, breaking of electrodes arose in the internal electrode layers andthe capacitance became low as 0.74 μF.

It was confirmed that as a result that a conductive component and adielectric component were included in the pre-fired internal electrodethin film and a content of the dielectric component in the internalelectrode thin film is larger than 0 wt % but not larger than 3 wt %with respect to the entire internal electrode thin film, spheroidizingin the internal electrode layers and breaking of electrodes were able tobe prevented effectively and a decline of the capacitance could besuppressed even when the fired internal electrode layers were madethinner. Note that it was confirmed that it is preferably larger than 0wt % but not larger than 3 wt % in the case of Yb₂O₃ and, from theresults of the example 4 below, it is considered that the same resultscan be obtained in the case of MgO, Al₂O₃, SiO₂, CaO, TiO₂, V₂O₃, MnO,SrO, Y₂O₃, ZrO₂, Nb₂O₅, BaO, HfO₂, La₂O₃, Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃,Er₂O₃, Tm₂O₃, Yb₂O₃, Lu₂O₃, CaTiO₃ or SrTiO₃.

Example 4

Other than using MgO, Al₂O₃, SiO₂, CaO, TiO₂, V₂O₃, MnO, SrO, Y₂O₃,ZrO₂, Nb₂O₅, BaO, HfO₂, La₂O₃, Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃, Er₂O₃, Tm₂O₃,Yb₂O₃, Lu₂O₃, CaTiO₃ or SrTiO₃ instead of BaTiO₃ as a dielectric targetwhen forming the pre-fired internal electrode thin film 12 a, sampleswere obtained in the same way as in the example 1. Evaluation ofelectric characteristics (capacitance C and dielectric loss tan δ) wasmade on each sample in the same way as in the example 1. The results areshown in Table 3. Evaluation of the electric characteristics(capacitance C and dielectric loss tan δ) was made in the same way as inthe example 1.

TABLE 3 Pre-Fired Internal Electrode Thin Film 12a Content ContentSample Thickness Ratio of Ratio Capacitance No. [μm] Nickel Added Oxide[wt %] [μF] tan δ Evaluation 11 Example 0.4 99.5 MgO 0.5 0.95 0.02 ◯ 12Example 0.4 99.5 Al2O3 0.5 0.97 0.02 ◯ 13 Example 0.4 99.4 SiO2 0.6 0.950.04 ◯ 14 Example 0.4 99.4 CaO 0.6 0.95 0.03 ◯ 15 Example 0.4 99.4 TiO20.6 0.97 0.02 ◯ 16 Example 0.4 99.3 V2O3 0.7 0.95 0.04 ◯ 17 Example 0.499.4 MnO 0.6 0.96 0.02 ◯ 18 Example 0.4 99.4 SrO 0.6 0.95 0.04 ◯ 19Example 0.4 99.2 Y2O3 0.8 0.97 0.03 ◯ 20 Example 0.4 99.4 ZrO2 0.6 0.950.02 ◯ 21 Example 0.4 99.4 Nb2O5 0.6 0.94 0.04 ◯ 22 Example 0.4 99.3 BaO0.7 0.94 0.04 ◯ 23 Example 0.4 99.3 HfO2 0.7 0.95 0.05 ◯ 24 Example 0.499.4 La2O3 0.6 0.96 0.03 ◯ 25 Example 0.4 99.4 Gd2O3 0.6 0.96 0.03 ◯ 26Example 0.4 99.4 Tb4O7 0.6 0.96 0.03 ◯ 27 Example 0.4 99.4 Dy2O3 0.60.96 0.03 ◯ 28 Example 0.4 99.4 Ho2O3 0.6 0.96 0.03 ◯ 29 Example 0.499.4 Er2O3 0.6 0.96 0.03 ◯ 30 Example 0.4 99.4 Tm2O3 0.6 0.96 0.03 ◯ 31Example 0.4 99.4 Yb2O3 0.6 0.96 0.03 ◯ 32 Example 0.4 99.4 Lu2O3 0.60.96 0.03 ◯ 33 Example 0.4 99.3 CaTiO3 0.7 0.97 0.02 ◯ 34 Example 0.499.3 SrTiO3 0.7 0.97 0.02 ◯

Table 3 shows a thickness of a pre-fired internal electrode thin film 12a formed for each sample, a content ratio of nickel and added respectiveoxides explained above, capacitance, dielectric loss tan δ andevaluation on each sample.

As shown in Table 3, all of samples in the example, wherein thepre-fired internal electrode thin film 12 a includes nickel as aconductive component and respective oxides explained above as adielectric component and a content ratio of the oxides was respectivelyas shown in Table 3 (wt %), exhibited preferable results that thecapacitance exceeded 0.9 μF and the dielectric loss tan δ became lessthan 0.01.

It was confirmed that as a result that a conductive component and adielectric component were included in the pre-fired internal electrodethin film and a content of the dielectric component in the internalelectrode thin film is larger than 0 wt % but not larger than 3 wt %with respect to the entire internal electrode thin film, spheroidizingin the internal electrode layers and breaking of electrodes were able tobe prevented effectively and a decline of the capacitance could besuppressed even when the fired internal electrode layers were madethinner.

1. A production method of an electronic device for producing anelectronic device including internal electrode layers and dielectriclayers, comprising the steps of: forming a pre-fired internal electrodethin film including a conductive component and a dielectric component;stacking a green sheet to be a dielectric layer after firing and saidpre-fired internal electrode thin film; and firing a multilayer body ofsaid green sheet and said pre-fired internal electrode thin film;wherein a content of said dielectric component in said pre-firedinternal electrode thin film is larger than 0 mol % but not larger than0.8 mol % with respect to the entire pre-fired internal electrode thinfilm.
 2. The production method of an electronic device as set forth inclaim 1, wherein said dielectric component in said pre-fired internalelectrode thin film includes at least one kind of BaTiO₃, Y₂O₃ and HfO₂.3. A production method of an electronic device for producing anelectronic device including internal electrode layers and dielectriclayers, comprising the steps of: forming a pre-fired internal electrodethin film including a conductive component and a dielectric component;stacking a green sheet to be a dielectric layer after firing and saidpre-fired internal electrode thin film; and firing a multilayer body ofsaid green sheet and said pre-fired internal electrode thin film;wherein a content of said dielectric component in said pre-firedinternal electrode thin film is larger than 0 wt % but not larger than 3wt % with respect to the entire pre-fired internal electrode thin film.4. The production method of an electronic device as set forth in claim3, wherein: said dielectric thin film in said pre-fired internalelectrode thin film includes at least one kind of BaTiO₃, MgO, Al₂O₃,SiO₂, CaO, TiO₂, V₂O₃, MnO, SrO, Y₂O₃, ZrO₂, Nb₂O₅, BaO, HfO₂, La₂O₃,Gd₂O₃, Tb₄O₇, Dy₂O₃, Ho₂O₃, Er₂O₃, Tm₂O₃, Yb₂O₃, Lu₂O₃, CaTiO₃ andSrTiO₃.
 5. The production method of an electronic device as set forth inclaim 1, wherein a thickness of said pre-fired internal electronic thinfilm is 0.1 to 1.0 μm.
 6. The production method of an electronic deviceas set forth in claim 1, wherein said pre-fired internal electronic thinfilm is formed by a thin film formation method.
 7. The production methodof an electronic device as set forth in claim 6, wherein said thin filmformation method is the sputtering method, vapor deposition method orcomposite plating method.
 8. The production method of an electronicdevice as set forth in claim 7, wherein said pre-fired internalelectrode thin is formed by performing sputtering of a metal materialand an inorganic material for composing said conductive component andsaid dielectric component at a time.
 9. The production method of anelectronic device as set forth in claim 8, wherein an inert gas is usedas an introduction gas and a gas introduction pressure of said inert gasis 0.01 to 2 Pa when performing said sputtering.
 10. The productionmethod of an electronic device as set forth in claim 1, wherein adielectric component included in said pre-fired internal electrode thinfilm and said green sheet include dielectric having substantially thesame composition.
 11. The production method of an electronic device asset forth in claim 1, wherein an average particle diameter of adielectric component included in said pre-fired internal electrode thinfilm is 1 to 1 0 nm.
 12. The production method of an electronic deviceas set forth in claim 1, wherein a conductive component included in saidpre-fired internal electrode thin film is nickel and/or a nickel alloyas its main component.
 13. The production method of an electronic deviceas set forth in claim 1, wherein said multilayer body is fired in anatmosphere having an oxygen partial pressure of 10⁻¹⁰ to 10⁻² Pa at atemperature of 1000° C. to 1300° C.
 14. The production method of anelectronic device as set forth in claim 1, wherein after firing saidmultilayer body, annealing is performed in an atmosphere having anoxygen partial pressure of 10⁻² to 100 Pa at a temperature of 1200° C.or lower.
 15. An electronic device produced by any one of the methods asset forth in claim
 1. 16. A production method of a multilayer ceramiccapacitor having an element body, wherein internal electrode layers anddielectric layers are alternately stacked, comprising the steps of:forming a pre-fired internal electrode thin film including a conductivecomponent and a dielectric component; alternately stacking green sheetsto be dielectric layers after firing and said pre-fired internalelectrode thin films; and firing a multilayer body of said green sheetsand said pre-fired internal electrode thin films; wherein a content ofsaid dielectric component in said pre-fired internal electrode thin filmis larger than 0 mol % but not larger than 0.8 mol % with respect to theentire pre-fired internal electrode thin film.
 17. A production methodof a multilayer ceramic capacitor having an element body, whereininternal electrode layers and dielectric layers are alternativelystacked; comprising the steps of: forming a pre-fired internal electrodethin film including a conductive component and a dielectric component;alternately stacking green sheets to be dielectric layers after firingand said pre-fired internal electrode thin films; and firing amultilayer body of said green sheets and said pre-fired internalelectrode thin films; wherein a content of said dielectric component insaid pre-fired internal electrode thin film is larger than 0 wt % butnot larger than 3 wt % with respect to the entire pre-fired internalelectrode thin film.
 18. A multilayer ceramic capacitor produced byeither one of the methods as set forth in claim 16.